pythongh-99942: correct the pkg-config/python-config flags for cygwin…

…/android

On shared build configurations, Cygwin and Android need to link to
libpython. See bpo-21536.

This was corrected in distutils with an explicit check to only link when
libpython is built shared, but implemented in configure.ac
unconditionally. The correct approach is to follow distutils, which
includes a comment regarding why:
- on Android, a shared libpython is RTLD_LOCAL, and thus available only
  to the main executable, not exported to loaded modules, but a static
  libpython *is* the main executable and thus exported

configure.ac

@@ -5827,7 +5827,7 @@ AC_MSG_RESULT($LDVERSION)
 
 # On Android and Cygwin the shared libraries must be linked with libpython.
 AC_SUBST(LIBPYTHON)
-if test -n "$ANDROID_API_LEVEL" -o "$MACHDEP" = "cygwin"; then
+if test "$PY_ENABLE_SHARED" = "1" && ( test -n "$ANDROID_API_LEVEL" || test "$MACHDEP" = "cygwin"); then
   LIBPYTHON="-lpython${VERSION}${ABIFLAGS}"
 else
   LIBPYTHON=''